Triplk stage upright for lift tkuck

ABSTRACT

THIS INVENTION RELATES GENERALLY TO A TRIPLE-STAGE TELESCOPIC EXTENSIBLE UPRIGHT OR MAST ASSEMBLY SUPPORTED FROM THE TRUCK AND SUPPORTING A LIFT FORK OR OTHER LOAD ENGAGING MEANS EMPLOYED WITH SUCH TRUCKS. MORE SPECIFICALLY, THE INVENTION COMPRISES AN IMPROVEMENT IN TRIPLE-STAGE UPRIGHT CONSTRUCTIONS OF THE TYPE DISCLOSED IN PATENT NO. 3,213,967.

Aug. 14, 1973 R. F. MCINTOSH 27,731

TRIPLE STAGE UPRIGHT FOR ETFT TRUCK 5 Sheets-Sheet 1 Original Filed May18, 1964 WVENTOR RICHARD F M ENTOSH ATHJRNFY Aug. 14, R. F. Mv 5 Re.

5 Shouts-Sheet .1

Original Filed May 18, 196-1 IYVFNTOR RICHARD F. MUNTOSH ATTORNEY g-1973 R. F. MCINTOSH 27,731

TRIPLE-l STAGE UFRIGHT FOR LIFT TRUCK Original Filed May 18, 1964 5Sheets-Sheet I:

RICHARD F MCENTOSH p ATTORNEY Aug. 14, 1973 R. F. MqNTQSH Re. 27,731

5 Sheets-Sheet 4 Original Filed May 18, 1964 NVEXTOR RICHARD F MC INTOSHATTORNEY TRIPLE STAGE UFRIUHT FOR LEFT TRUCK 5 Sheets-Sheet F OriginalFiled May .8, 1964 F M INTOSH RICHARD ATTORNE r United States Patent27,731 TRIPLE STAGE UPRIGHT FOR LIFI TRUCK Richard F. McIntosh, BattleCreek, Mich., assignor to Clark Equipment Company Original No.3,298,463, dated Jan. 17, 1967, Ser. No. 368,064, May 18, 1964.Application for reissue Feb. 16, 1971, Ser. No. 115,895

Int. Cl. 1366b 9/20 U.S. Cl. 187-9 6 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE In lift truck uprights of the typecontemplated it has long been a problem to provide a construction whichaffords the operator of the truck good visibility through the uprightwhen the load engaging means is at or near floor level. My inventionprovides a novel combination of telescopic upright structure, telescopichydraulic lifting ram or cylinder structure, and dual lifting chainstructure on each side of the upright which together provide a compactstructure hvaing a relatively low collapsed height, high maximumelevation, and affords substantially improved operator visibility. It istherefore a principal object of the present invention to provide animproved triple-stage telescopic upright structure which affordsexcellent operator visibility through the structure.

It is another object of the invention to provide in lift truck uprightsan improved combination of lifting elements, such as chains, combined inthe upright and reeved in such a manner that maximum utility of theupright is effected.

Another object of the present invention is to provide in triple-stageuprights for lift trucks lifting elements, such as chains, wherein apair thereof are disposed on each side of a lift cylinder, one of eachpair of lifting elements being reeved on sprocket or wheel means havingan axis transverse of the truck and the other of each of said pairs oflifting elements being reeved on sprocket or wheel means having an axislongitudinal of the truck, whereby to provide a combination of liftingelements which minimizes interference with operator visibility throughthe upright.

Other objects, features and advantages of the invention will readilyappear to persons skilled in the art from the detailed description ofthe invention which follows.

Specifically, in carrying out the invention, there is provided a maststructure comprising laterally spaced-apart stationary uprights securedto the lift truck. Such uprights receive in forwardly offset nestedrelation in laterally spaced-apart pair of extensible uprights each ofwhich is preferably I-shaped in cross-section, and which latterextensible uprights receive also in forwardly offset nested relation asecond laterally spaced-apart pair of extensible uprights each of whichis also preferably I- shaped in cross-section. The load carriage isarranged to move up and down in the inner extensible uprights, and setsof rollers are provided between each pair of uprights and between theinner pair of uprights and the load carriage in order to provide fullstructural support both Re. 27,731 Reissuecl Aug. 14, 1973longitudinally and laterally of the truck during the raising andlowering of the load carriage and the extensible uprights. A preferredconstruction of rollers, as aforesaid, is disclosed in detail in saidaforementioned co-pending application of Hastings and Backofen. Avertically extending telescopic hydraulic ram structure is mountedcentrally of the upright from the lower end of the first extensibleupright. An intermediate cylinder of the telescopic ram assembly carriesa pair of transversely spaced sprocket members, over which are reeved apair of transversely spaced chains anchored at their one ends to theouter cylinder member of the ram structure and at the opposite ends tothe load carriage. The first pair of sprocket means rotates on an axistransverse of the truck. A second pair of sprocket means are mounted intransversely spaced relation adjacent the lower end of the firstextensible upright and are adapted to rotate about axes longitudinal ofthe truck. A second pair of lifting chains are preferably secured attheir one ends to the outer cylinder of the telescopic ram and at theiropposite ends adjacent the upper ends of said stationary uprights.

In the accompanying drawings, there is illustrated a preferredembodiment of the invention wherein:

FIGURE 1 is a front view of an industrial lift truck showing the loadcarriage lowered to the bottom of the inner extensible upright, andexemplifying the good operator visibility which is provided through theupright construction;

FIGURE 2 is an enlarged rear view of that portion of the upright shownin FIG. 1 which extends above the front portion of the truck, and showsa portion of the operators compartment, all as viewed from behind theoperators seat on the truck;

FIGURE 3 is a full rear view of the upright shown in FIG. 1 with theentire upright assembly dismounted from the truck and the load carriageat floor level;

FIGURE 4 is a view of the upright as shown in FIG. 3 with the loadcarriage elevated to a position adjacent the upper end of the retractedupright assembly;

FIGURE 5 is a rear view of the upright assembly shown in the precedingfigures, on a somewhat smaller scale, showing the entire assembly in aposition of intermediate elevation with both pairs of extensibleuprights in partially elevated position;

FIGURE 6 is a broken-away rear view of the upright assembly, as is FIG.5, in a position of maximum elevation of both the load carriage and theextensible uprights;

FIGURE 7 is a view of the upright taken from above with the loadcarriage in the position shown in FIG. 4; and

FIGURE 8 is a broken-away partial longitudinal sectional view of thetelescopic ram structure which is utilized in the upright.

Referring now in detail to the drawings, a conventional industrial lifttruck is shown at numeral 10 having a frame and body construction 12mounted on a pair of steering wheels, not shown, at the rear end thereofand a pair of traction wheels 14 forwardly thereof, and embodyingsuitable power components, which may be either electric or gas, foroperating the truck from an operator's compartment 16, which includes anoperators scat mounted above the engine compartment, opcrators footcontrols, such as accelerator pedal and brake, not shown, and aplurality of hand controls and instrumentation, such as is shown in FIG.2, including a steering wheel 18, a control lever 20 for operating theupright and a power train control lever supported from the steeringpost. An operator is illustrated in FIG. 1 at numeral 22 as he wouldappear to an observer in .front of the truck when seated on the truck ina normal position for driving the truck.

The upright assembly of the present invention is illustrated generallyat numeral 30, the assembly being monuted on the truck by means of apair of rearwardly extending support plate 32 secured to a lower fixedtransverse plate 34 of the upright assembly and adapted to be pivotablymounted by means of openings 36 thereof upon bearing portions of thedrive axle, not shown. Brackets 42 secure the upper end of plates 32 toa lower fixed mast section 38 which includes a pair of transverselyspaced opposed channel members 40 of substantially C-shapedcross-section. Channel members 40 are arranged to receive anintermediate mast section 44 formed of two laterally spaced I-beams 46,the intermediate mast section 44 being roller supported and arranged forlongitudinal movement relative to the stationary mast section 38, aswill be hereinafter described. In addition to the intermediateextensible section 44, an inner extensible mast section 48 is formed oftwo laterally spaced I- beams 50 which are telescopically arrangedinwardly of I-beams 46 for longitudinal movement relative to thestationary mast section 38 and to the intermediate mast section 44, theinner mast 48 being roller supported and arranged for longitudinalmovement relative to the intermediate section 44. A load or forkcarriage 51 is roller mounted for elevation in a well-known manner ininner mast section 48. A bracket 52 extends rearwardly of each channelmember 40 and is adapted to be connected to hydraulic upright tiltcylinder means, not shown, carried by the truck for tilting the uprightlongitudinally of the truck.

Mast section 38 is cross-braced for rigidity by means of transversebrace members 35 and 54 (which are in addition to lower brace member34), intermediate mast section 44 is cross-braced by means of upper,central and lower transverse braces 56, 58 and 60, respectively, andinner mast section 48 is cross-braced by upper, central and lower bracemembers 62, 64 and 66, respectively. The upper cross-braces of therespective mast sections are arranged in vertically spaced relation toeach other so that there is no interference therebetween, as shown inthe figures, and the braces 64 and 66 of the inner mast and 58 and 60 ofthe intermediate mast are arranged so that they can pass inside of thevarious other cross braces during extension and reaction of the upright,as shown in the figures.

The inner I-beam mast section 48 is nested within intermediate mastsection 44 in such a manner that the forward flange of I-beams 50 aredisposed outside of the forward flange of I-beams 46, and the rearwardflanges of I-beam 50 are disposed within the adjacent channel portionand forwardly of the rearward flanges of I-beams 46, sets of rollersbeing suitably mounted between said adjacent pairs of nested I-beams 46and 50 for supporting each of the I-beams 50 longitudinally andlaterally for extensible movement relative to the adjacent I-beam 46.The upper rollers of each said set are illustrated at 70 in FIG. 7.Similarly, I-beams 46 of the first extensible mast section 44 are nestedin forwardly offset overlapping relation in respect of the flangeportions of outer fixed channel members 40 of mast section 38, and arealso mounted for telescopic movement outwardly of channel members 40upon sets of rollers which support I-beams 46 longitudinally andlaterally relative to channel beams 40. The upper rollers of said latterroller sets are illustrated at numerals 72. Cutouts 74 are provided atthe upper ends of channel beams, and cutouts 76' are provided at theupper ends of I-beams 46 (FIG. 1) so that the rollers may be mountedwithin the respective mast sections prior to assembly thereof, thecutouts in the upper ends of the flanges providing for by-passing of therollers during assembly of the upright sections, and making availablethe use of relatively large diameter rollers 72 and 70 which extendthrough the respective cutout flange portions, said rollers beingmounted upon the rear ends of upright beams 40 and 46 respectively.

The load carriage 51 is mounted in a well-known manner forwardly of theupright assembly, having a pair of transversely spaced fork bar members80 (FIG. 7) secured to the load carriage and having mounted thereonupper and lower pairs of rollers, the upper rollers being shown atnumeral 82, which supports the load carriage for extensible movementwithin the inner channel portions of I-beams 50. A pair of side thrustrollers 84 are connected to the load carriage and are adapted to rollalong the outer offset edge portion of each inner I-beam member 50, saidpair of side thrust rollers 84 cooperating with the inner carriagesupport rollers 82 for preventing a tendency of the upright to spreadapart or wedge when the load carriage is eccentrically loaded, and forresisting side thrust forces imposed upon the load carriage. Theparticularities of the nested offset I-beam upright structure, themounting of the load carriage thereon and the manner of providing rollersets as aforesaid is explained in detail in the above-mentionedco-pending application, and need not be detailed further in thisapplication. The importance of the forwardly offset nested uprightstructure in the present application is that such upright structurecombines with my novel chain reeving structure to provide an improvedupright, as will become apparent as the description proceeds.

A multiple cylinder telescopic hydraulic ram assembly is shown generallyat numeral (FIG. 8). It comprises essentially five hollow tubularmembers in concentric sliding relation wherein the inner tubular member92 is secured at its base end 94 to fixed brace 34 at the bottom offixed upright 38 and is adapted to be connected to fluid pressure pumpmeans by a flexible conduit, not shown, at 96, thereby serving as arigid upright conduit for communicating pressure fluid to and from thehydraulic ram assembly 90 through a controlled valve means 98 at theupper end of the inner tube 92, the tube 92 being of somewhat lesslength than outer upright section 38. An inner structural tubular member100 is fixedly mounted at the lower end thereof to transverse bracemember 60- at the lower end thereof intermediate beams 46, being open atboth the top and bottom, having sealing means 102 slidable on the wallof inner tubular conduit 92, and a stop member 104 which is adapted toabut a stop 106 on conduit 92 when the tube 100 is fully extended, as inFIG. 6. An integral inner-outer tubular ram construction 10-8, 110 isthreadedly secured at 112 to function as a single telescopic ram unit,and encompasses tube 100, inner tube 108 thereof being slightly less inlength than the height of outer mast section 40 and having a closed headend 114 which is suitably connected at 116 to the upper transverse brace62 of inner mast section 48. Nested within the longitudinal annularspace provided between tubular members 108 and 110 is an intermediatehydraulic tubular ram 120 which is approximately one-half the length ofouter upright section 3 8 and upon the upper end of which is mounted across head 122 to which is connected in transversely spaced relation 21pair of sprocket members 124 which are mounted for rotation on outwardlyextending stub shaft members 125 about an axis transverse of theupright. Suitable annular packing seals are provided at 126- at theupper end of outer tube 110, at 128 at the lower end of inner elevatabletube 100, and at 130 at the upper cross head end of intermediatetelescopic tube 120. Pairs of stop means are suitably located at theupper and lower ends of adjacent telescopic tube members for limitingthe extension of one relative to the other. A plurality ofcircumferential openings are provided at 132 in tubular conduit 92, at134 in the inner tube 100, and at 136 in inner telescopic tube 108 forcommunicating the various longitudinal annular spaces between therespective adjacent pairs of tubular members one with another.

An anchor plate 140 is secured, as by welding, to the outer tube 110.Plate 140 includes a pair of transversely extending ear portions 142which extend from opposite sides of plate 140 and a pair of rearwardlyprojecting ear portions 144. A first pair of transversely spaced chainmembers 146 are reeved over sprockets 124 on cross head 122 and securelyanchored at their one ends to load carriage 51. Chains 146 are anchoredat their opposite ends to ears 142 of anchor plate 140 by means of apair of long bolts 148 which extend through openings in the ear membersand are secured thereto by nuts threaded on the ends of the bolts. Thus,the pair of chains 146 are adapted, in the first stage of elevation ofthe upright upon communication of pressure fluid to the telescopic ramassembly 90, to elevate load carriage 51 from the ground level positionshown in FIG. 3 to a full free-lift position, as shown in FIG. 4, asintermediate cylinder ram 120 is initially actuated upwardly along innerextensible tube 108, thereby actuating cross head 122 and sprockets 124to elevate the load carriage at a 2:1 ratio of movement to cylinder 120to effect such full free-lift movement of the load carriage whiletelescopic mast sections 44 and 48 remain fully collapsed within outermast section 38. With the load carriage in a full free-lift positioncylinder 120 is fully extended relative to cylinder 108 and stop membersat the lower end of cylinder 120 contact stop members at the upper endof outer cylinder 110. Pressure fluid acts on an area at the bottom ofinner-outer cylinder assembly 108, 110 to hold said assembly down duringextension of cylinder 120, and anchor plate 140 thus remains in a fixeddown position, as shown in FIGS. 3 and 4.

A second pair of transversely spaced chains 150 are located at rightangles to chain 146 and generally rearwardly thereof, being located insubstantially co-planar relation in a plane which extends transverselyof the truck and reeved on a pair of transversely spaced sprockets 152which are mounted on stub shafts for rotation at the lower end ofintermediate mast section 44 on brace 60 and which are adapted forrotation about axes which extend longitudinally of the truck. The oneends of chains 150 are anchored by long bolts 154 to rearwardlyextending ears 144 of anchor plate 140. The opposite ends of chains 150are fixed secured to upper transverse brace 53 adjacent the upper end ofouter fixed mast section 38 by a pair of transversely spaced brackets158 (FIG. 2) which are nested behind the rear flanges of the I-beams 46of intermediate mast 44 and which extend inwardly and forwardly of bracemember 53 so as to provide said substantially co-planar relation ofchains 150 and a nesting of the upwardly extending lengths of the pairof chains, as shown in FIGS. 2-5, behind the flanges of the innerI-beams 50. The forwardly offset nested relation of the telescopic mastsections 44 and 48 relative to each other and to outer mast section 38provide space as required to compactly and efficiently nest the pair ofchains 150 behind the upright and the ram cylinder construction so thatsaid pair of chains 150 does not interfere to any substantial designwith operator visibility through the upright when the load carriage isin any position from ground level to maximum elevation thereof.

Operation during the second phase of lifting from the position ofelevation of the load carriage shown in FIG. 4 to maximum elevationthereof, as shown in FIG. 6, is as follows; continued communication ofpressure fluid with ram cylinder assembly 90 effects extension ofinner-outer tube assembly 108, 110 together with intermediate cylinder120 outwardly relative to inner ram cylinder 100, and elevation of thelatter ram cylinder with the intermediate mast section 44 and outwardlyalong pressure feed conduit 92. As pressure fluid continues to besupplied to the ram assembly with the load carriage in the positionshown in FIG. 4, simultaneous extension of the intermediate cylinder 120and inner-outer cylinder assembly 108, 110 causes the anchor plate onthe outer cylinder 110 to be elevated therewith, which applies tensionto the pair of chains 150 such that said chains cause simultaneouslyelevation of intermediate mast section 44 out of outer mast 38, which inturn elevates simultaneously inner ram cylinder on feed cylinder conduit92, since cylinder 100 is mounted upon the transverse brace 60 near thebottom end of the intermediate mast section. It will be apparent that asthe intermediate mast section is elevated by the chain action 150 asaforesaid inner mast section 48 is being simultaneously telescopedoutwardly of intermediate mast section 44, and the net results is thatthe telescopic mast sections 48 and 46 are telescope outwardlysimultaneously from the FIG. 4 position to an intermediate elevation, asshown in FIG. 5, and thence to the maximum extension shown in FIG. 6.Throughout such elevation chain members 146 maintain the load carriage51 adjacent the upper end of inner mast 48, and the telescopic ramassembly acting through the intermediate mast 44 by means of chains 150and sprockets 152 effects such extension of the telescopic mast sectionsin relation to fixed mast section 38. Thus, a smooth and continuouselevation of the load carriage 51 is effected from ground level tomaximum elevation at a constant speed of elevation, which is desirable.

Heretofore, to applicants knowledge, in the telescopic upright art notriple-stage upright has been devised which is capable of a fullfree-lift load carriage operation and at the same time affords goodoperator visibility throughout the lifting cycle. In the FIG. 1illustration, it will be noted that whenever the load carriage is in aload carrying position, i.e., with the load carriage elevated slightlyabove ground level, the operator has picture window visibility throughthe upright. During elevation from ground level to maximum elevation ofthe load carriage, chain members 150 never afford any significant degreeof interference with operator visibility, and this has not heretofore,to applicants knowledge, been achieved in such an upright construction.Again, as previously noted, chain members 150 are continuously nestedbehind flanges of the inner mast section 48 of substantially behindtubular elements of the cylinder ram assembly, so that these chainsnever interfere to any substantial degree with operator vision. In thefull freelift triple-stage upright construction of the prior art thisresult has never been achieved.

Although it is within the scope of the invention to provide chainreeving as described above in roller type uprights which do not provideforwardly offset mast sections in a direction longitudinal of the truckfor reeving of part of the chains behind flange portions of the mastsections, as previously described. It may be possible to also utilize achain reeving construction in sliding type upright not utilizing rollermounted mast sections, although such an arrangement is not believed tobe economically feasible or practical. It should be understood thatchain members 150 can be anchored at the inner transversely spaced endsthereof not only to an anchor 140 located on the outer cylinder member110, but also can be readily anchored in a fully equivalent manner toanchor portions which can be connected to, for example, transverse brace64 of inner mast section 48, inasmuch as the outer cylinder and innermast section 48 have no relative vertical movement to each other at anytime.

Although I have described and illustrated a preferred embodiment of myinvention, it will be understood by those skilled in the art thatmodifications may be made in the structure, form and relativearrangements of parts without departing from the spirit and scope of theinvention. Accordingly, it should be understood that I intend to coverby the appended claims all such modifications which fall within thescope of my invention.

I claim:

1. A mast structure for lift trucks comprising outer, intermediate andinner flanged upright sections in telescoping relation to each other, aload carriage mounted on and movable along said inner upright section,an expansion unit having first, second and third relatively expansibleand concentric elements, said first element being connected to saidintermediate upright section, said second element being connected tosaid inner upright section, and said third element being connected tosaid load carriage and movable along said second element, a pair oftransversely spaced sheave means mounted on said third element forrotation about an axis transverse of the truck, a pair of secondtransversely spaced sheave means mounted rotatably on said intermediateupright section at the lower end portion thereof for rotation aboutrespective ones of a pair of transversely spaced longitudinallyextending axes, a pair of first chain means operatively connected at theone ends thereof to the inner upright section, passing over respectiveones of the first pair c sheave means and connected at the opposite endsto said load carriage, and a pair of second chain means operativelyconnected at the one ends thereof to said inner upright section, passingunder the opposite ones of said second sheave means in oppositedirection for separate connection adjacent the upper end portion of saidouter upright section, said inner upright section being offset forwardlyof said intermediate upright section to provide an open vertical spacebetween the rear [flanges] of each side of said inner and intermediateupright sections, said pair of second chain means each having avertically extending portion disposed at least partially in respectiveones of said spaces closely adjacent to and behind the rear [end]flanges of the respective sides of said inner upright section, the chainreeving of said pair of second chain means providing minimuminterference with visibility through the mast assembly during operationthereof.

2. A mast assembly as claimed in claim 1 wherein [said] [second pair ofsheave means are adapted to roate in a substantially common transverseplane and have a greater transverse spacing between the center thereofthan the center spacing of said first pair of sheave means] a fourthrelatively expansible concentric element is secured to said second suchelement and is movable therewith in relation to said third such element,said second and fourth elements and inner upright section being immovable relative to each other.

3. A mast assembly for a lift truck comprising first, second and thirdflanged upright sections, said second section being mounted for verticalmovement on said first section, said third section being mounted forvertical movement on said second section, a load carriage mounted forvertical movement along said third section, a cylinder assembly mountedbetween said second and third sections, said assembly having a firsthydraulic cylinder substantially the length of one of the uprightsections connected to said second section, a second hydraulic cylinderslideable on the said first cylinder, connected to the third section andhaving a length substantially the length of one of the upright sections,a third hydraulic cylinder substantially one-half the length of one ofthe upright sections and slidable on the second cylinder and a fourthhydraulic cylinder secured to said second cylinder and slidable inrelation to said third cylinder, said fourth cylinder and third uprightsection being immovable relative to each other, anchor means secured tosaid fourth cylinder, first sprocket means mounted at the upper end ofthe third cylinder and rotatable about an axis transverse of the truck,first chain means extending over said sprocket means and connected atone end to the load carriage, second spocket means mounted at the lowerend of said second upright section and rotatable about an axislongitudinal of the truck, and second chain means extending beneath saidsecond sprocket means and connected at one end thereof to the upper endportion of the first upright section, the opposite ends of said firstand second chain means being secured to said anchor means, one of saidupright sections being ofiset in a forward direction relative to anadjacent section whereby to provide a vertical space in a directionforwardly of the truck between the rear flanges of said latter uprightsections, a portion of the second chain means being disposed at leastpartially in said vertical space closely adjacent to and behind the rearflange of said one upright section.

[4. A mast structure for lift trucks comprising outer, lntermediate andinner upright sections in telescoping relation to each other, a loadcarriage mounted on and movable along said inner upright section, anexpansion unit having first, second, third and fourth expansible andconcentric elements, said first element being connected to saidintermediate upright section, said second element being connected tosaid inner upright section, and to said fourth element, and said thirdelement being connected to said load carriage and movable along saidsecond element, said fourth element and inner upright section beingimmovable relative to each other, anchor means secured to said fourthelement, first sheave means mounted on said third element for rotationabout an axis transverse of the truck, second sheave means mounted onsaid intermediate upright section for rotation about an axislongitudinal of the truck, first chain means connected to said anchormeans, passing over the first sheave means and connected to said loadcarriage, and second chain means connected to said anchor means, passingunder said second sheave means and connected to the upper end portion ofsaid outer upright section] 5. A mast structure for lift truckscomprising outer, intermediate and inner flanged upright section intelescoping relation to each other, a load carriage mounted on andmovable along said inner upright section, [one of] said inner upright[sections] section being offset forwardly of [another of] said uprightsection-[s] to provide a vertical forwardly extending space between therear [ends] flanges of said latter upright section, an expansion unithaving first, second, [and] third and fourth expansible and concentricelements, said first element being connected to said intermediateupright section, said second element being connected to said innerupright section and to said fourth element [and] said third elementbeing connected to said load carriage and movable along said secondelement, said second and fourth elements and said inner upright sectionbeing immovable relative to each other a first pair of transverselyspaced sheave means mounted on said third element for rotation about anaxis transverse of the truck, a second sheave means mounted on saidintermediate upright section for rotation in a substantially commonplane about [an axis] longitudinal of the truck having a greatertransverse spacing than the spacing between the centers of said firstpair of sheave means, first chain means operatively connected at one endto the inner upright section, passing over the first sheave means andconnected at the opposite end to said load carriage, and second chainmeans operatively connected at one end to said inner upright section,passing under said second sheave means and connected at the opposite endto the upper end portion of said outer upright section, said secondchain means having a vertically extending portion thereof disposed atleast partially in said vertical forwardly extending space closelyadjacent to and behind the rear flanges of said inner upright section,said chain reeving of said second chain means providing minimuminterference with visibility through the mast assembly during operationof the truck.

[6. A mat assembly as claimed in claim 5 wherein said second sheavemeans are adapted to rotate in a substantially common plane and have agreater transverse spacing between the centers thereof than said firstpair of sheave means] [7. A mast assembly for lift trucks comprisingfirst, second and third mast sections said second mast section beingmounted for vertical movement on said first mast section, said thirdmast section being mounted for vertical movement on said second mastsection, a load carriage mounted for vertical movement along said thirdmast section, a hoist cylinder assembly mounted between said second andthird mast sections, said assembly having a first hydraulic cylindersubstantially the length of one of the mast sections connected to saidsecond mast section, a second hydraulic cylinder slidable on said firstcylinder, connected to the third mast section and having a lengthsubstantially the length of one of the mast sections, a third hydrauliccylinder substantially one-half the length of one of the mast sectionsand slidable on the second cylinder, first sprocket means mounted at theupper end of the third cylinder and rotatable about an axis transverseof the truck, first chain means operatively connected at one end to thethird mast section, extending over said sprocket means and connected atthe other end to the load carriage, second sprocket means mounted at thelower end of said second mast section and rotatable about an axislongitudinal of the truck, and second chain means operatively connectedat one end to the third mast section, extending beneath said secondsprocket means and connected at the opposite end to the upper endportion of the first mast section, one of said mast sections beingoffset in a forward direction relative to an adjacent mast sectionwhereby to provide a vertical space in a direction forwardly of thetruck between the rear ends of said latter mast sections, a portion ofthe second chain means being disposed at least partially in saidvertical space] 8. A mast [assembly] as claimed in claim [7] 9 wherein[said first sprocket means comprises a pair of transversely spacedsprockets reevin g a pair of chains which comprises said first chainmeans, and said second sprocket means comprises a pair of transverselyspaced sprockets rotatable about transversely spaced longitudinal axesand reeving a pair of chains which comprises said second chain means]second chain means is connected to said anchor means transverselyinwardly of the connection thereto said first chain means.

9. A mast structure for lift trucks comprising first, second and thirdflanged mast sections in telescoping relation to each other, a loadcarriage mounted on and movable along said third mast section, anexpansion unit having first, second, third and fourth expansible andconcentric elements, said first element being connected to said secondmast section, said second element being connected to said third mastsection, said third element being connected to said load carriage andmovable along said sec ond element, and said fourth element beingconnected to said second element and slidable in relation to said thirdelement, said fourth element and third mast section being immovablerelative to each other, anchor means secured to said fourth element,first sheave means mounted on said third element for rotation about anaxis transverse of the truck, second sheave means mounted on said secondmast section for rotation about an axis longitudinal of the truck, firstchain means connected to the anchor means, passing over the first sheavemeans and connected to said load carriage, second chain means connectedto said anchor means, passing under said second sheave means andconnected to the upper end portion of the first mast section, one ofsaid mast sections being offset forwardly of another of said mastsection to provide a vertical forwardly extending space between the rear[ends] flanges of said latter mast sections, said second chain meanshaving a vertically extending portion thereof disposed at leastpartially in said vertical space closely adjacent to and behind the rearflanges of said third mast section so as to reduce interference withvisibility through the mast assembly during operation of the truck.

[10. A mast structure for lift trucks comprising outer, intermediate andinner mast sections in telescoping relation to each other, a loadcarriage mounted on and movable along said inner mast section, anexpansion unit having first, second and third relatively expansible andconcentric elements, said first element being connected to saidintermediate mast section, said second element being connected to saidinner mast section, and said third element being connected to said loadcarriage and movable along said second element, a first pair oftransversely spaced sheave means mounted on said third element forrotation about an axis transverse of the truck, a second pair of sheavemeans mounted on said intermediate mast section in transversely spacedrelation for rotation about transversely spaced longitudinally extendingaxes, first chain means operatively connected to the inner mast section,passing over the first pair of sheave means and connected to said loadcarriage, and second chain means operatively connected to the iner mastsection, passing under said second pair of sheave means outwardly inopposite direction for separate connection adjacent to the upper portionof said outer mast section, said chain reeving of said second chainmeans providing minimum interference with visibility through the mastassembly during operation of the truck] [11. A mast structure as claimedin claim 5 wherein said inner upright section is ofiset forwardly ofsaid intermediate upright section to provide said vertical forwardlyextending space between the rear ends of said inner and intermediateupright sections] [12. A mast assembly as claimed in claim 5 whereinsaid second sheave means comprises a pair of sheaves or sprocketsmounted in transversely spaced relation and rotatable about transverselyspaced longitudinal extending axes, and said second chain means includesa pair of chains which extend beneath opposite ones of said pair ofsheaves outwardly in opposite directions for separate connectionadjacent the upper end of said outer upright section, said chain reevingof said second chain means providing minimum interference withvisibility through the mast assembly during operation of the truck]References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 1,032,819 7/1912 Driscoll 187-17 3,053,050 9/1962Sommerer 18717 UX 2,987,140 6/1961 Olson 187-9 2,670,811 3/1954 Shaffer187-9 2,936,047 5/1960 Quayle 187-9 X 3,077,951 2/ 1963 Ramsey 187-93,208,556 9/1965 Shatter 187-9 FOREIGN PATENTS 1,041,864 10/ 1958Germany 187-9 1,115,009 4/1956 France 187-17 772,610 4/1957 GreatBritain. 966,123 5/ 1961 Great Britain.

EVON C. BLUNK, Primary Examiner M. F. MAFFEI, Assistant Examiner

